The invention relates to torque transmitting apparatus in general, and more particularly to improvements in axially and angularly yieldable elastic couplings which can transmit torque between misaligned rotary driving and driven units. Still more particularly, the invention relates to improvements in so-called plug-in axially and angularly yieldable elastic couplings wherein a flange-like component transmits torque to a hub-like component or vice versa through the medium of mating annuli of internal and external teeth.
Certain heretofore known elastic couplings which are used for transmission of torque between rotary driving and driven units whose axes are angularly and/or radially offset relative to each other and/or which move axially toward each other employ elastic rings which are subjected to torsional shearing stresses. Such rings are designed to compensate for pronounced radial displacement of the axes of driving and driven units relative to each other, and they are capable of transmitting relatively small restoring forces. The elastic rings of the just described conventional elastic couplings are installed between pairs of steel flanges which are secured to the driving unit. The flanges are further connected, normally by screws or bolts, with an internally toothed sleeve which serves to transmit torque to the driven unit by way of an externally toothed hub. The teeth of the hub are crowned in order to compensate for eventual inclination of the axes of rotation of the driving and driven units relative to each other. A drawback of such couplings is that the housing of the driving unit must be provided with openings for the aggregate including the steel flanges, the elastic ring between the flanges and the internally threaded sleeve which is bolted or screwed to the flanges. Moreover, the coupling cannot be fully assembled in the manufacturing plant, i.e., it is necessary to complete the assembly of the coupling at the locus of use in a time-consuming operation.
In accordance with another prior proposal, an axially and/or otherwise yieldable coupling for transmission of torque between misaligned rotary driving and driven units employs bolts or screws as a means for connecting a flange with a hub. The flange has an elastomeric ring which must take up all axial, radial and torsional stresses. A drawback of such couplings is that they must be installed between driving and driven units in a time-consuming operation. Moreover, the ring generates pronounced reaction forces when it is called upon to undergo compressive stresses, i.e., when its rigidity increases well above the average value.
Attempts to overcome the drawbacks of the just described prior couplings include the utilization of pins or studs which can be mounted at the radially innermost or at the radially outermost part of the coupling. The pins are insertable into a flange and into the part which is adjacent the flange in assembled condition of the coupling. Such pins and the holes or bores therefor must be machined with a high degree of precision which contributes to the initial cost of the coupling. The same applies for the making of the flange or flanges and of the adjacent parts. Moreover, it is necessary to provide the pins with layers of plastic material in order to reduce the likelihood of corrosion as a result of friction in actual use of the coupling. The pins are capable of compensating for axial movements of the driving and driven parts relative to each other. Angular displacements must be taken up by elastomeric parts which are provided in addition to the pins.
In accordance with still another prior proposal, the crowned teeth of the hub on the driven unit are placed into direct mesh with internal teeth of a plastic flange which, in turn, is directly affixed to the output element of the driving unit by screws or like fasteners. Such coupling exhibits the advantage that the housing of the driving unit need not be provided with an opening for the flange. The housing surrounds the outermost portion of the flange which can be placed into torque transmitting engagement with the hub as a result of insertion of the hub into the flange so that the crowned teeth of the hub mate with the internal teeth of the flange. A drawback of this coupling is that it does not permit any angular displacements of the hub and flange relative to each other. Moreover, the plastic flange is incapable of compensating for vibratory and other stray movements.